Conventional turbine casings may include one or more outer turbine casings that surround one or more inner turbine casings. The outer turbine casing is often split into two hemispherical casings bolted together by flanges on a horizontal plane to facilitate maintenance and repair. The inner turbine casing is often supported through to the outer turbine casing by one or more axially spaced circumferential arrays of pins.
Generally, active clearance controls are employed to radially displace inner and outer turbine casings from one another during transient turbine operations. This has the effect of controlling tip clearance between buckets and shrouds, which can be beneficial since decreasing tip clearance improves turbine performance by reducing tip leakage as long as bucket tips are prevented from transiently contacting and thereby rubbing shrouds.
With both active and passive systems in many configurations relative movement occurs between the inner and outer turbine casings due to differential thermal growth of their respective components. The aforementioned pins which are used to join the outer turbine casing with the inner turbine casing tangentially can reduce eccentricity caused by the relative movement. However, such pins can affect outer casing bolt spacing if the primary vertical support pins are placed near a preferred center-line supported configuration and thus intersect the outer casing bolted flange. Wider bolt spacing at the pinned locations can lead to horizontal joint overboard leakage and thus performance degradation.
Thus, a need exists for pins that allow for mounting of an inner turbine casing with an outer turbine casing without impacting outer turbine casing bolt spacing. Methods relating to such pins would also be beneficial.